Semiconductor constructions

ABSTRACT

The invention encompasses methods of forming metal nitride proximate dielectric materials. The metal nitride comprises two portions, with one of the portions being nearer the dielectric material than the other. The portion of the metal nitride nearest the dielectric material is formed from a non-halogenated metal-containing precursor, and the portion of the metal nitride further from the dielectric material is formed from a halogenated metal-containing precursor. The methodology of the present invention can be utilized for forming capacitor constructions, with the portion of the metal nitride formed from the halogenated metal-containing precursor being incorporated into a capacitor electrode.

This patent resulted from a continuation of U.S. patent application Ser.No. 10/887,962, which was filed Jul. 8, 2004, which issued as U.S. Pat.No. 7,148,118, and which is hereby incorporated by reference.

TECHNICAL FIELD

The invention pertains to methods of forming metal nitride, and inparticular aspects pertains to methods of forming capacitorconstructions.

BACKGROUND OF THE INVENTION

There are numerous applications for metal nitride in modernsemiconductor fabrication. For instance, metal nitride is frequentlyincorporated into capacitor electrodes. Problems can occur in utilizingvarious metal nitrides, and accordingly it is desired to develop newmethods for incorporating metal nitride into semiconductor structures,and in particular it is desired to develop new methods for incorporatingmetal nitride into capacitor structures.

SUMMARY OF THE INVENTION

In one aspect, the invention includes a method of forming a metalnitride proximate a dielectric material. A portion of the metal nitridenearest the dielectric material is formed from a non-halogenatedmetal-containing precursor without using halogenated metal-containingprecursor. A portion of the metal nitride furthest from the dielectricmaterial is formed from a halogenated metal-containing precursor.

In one aspect, the invention encompasses a method of forming a capacitorconstruction. A semiconductor substrate is provided, and a firstcapacitor electrode is formed over the semiconductor substrate. Adielectric material is formed over the first capacitor electrode. Afirst metal nitride layer is formed over the dielectric materialutilizing a non-halogenated metal-containing precursor. A second metalnitride layer is formed over the first metal nitride layer utilizing ahalogenated metal-containing precursor.

In one aspect, the invention encompasses a method of forming a capacitorconstruction in which a first capacitor electrode comprises a metalnitride layer formed from a halogenated metal-containing precursor. Asecond metal nitride layer is formed from a non-halogenatedmetal-containing precursor, and is formed over the first metal nitridelayer. A dielectric material is formed over the second metal nitridelayer, and a second capacitor electrode is formed over the dielectricmaterial.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

FIG. 1 is a diagrammatic, cross-sectional view of a semiconductor waferfragment at a preliminary processing stage of an exemplary firstembodiment aspect of the present invention.

FIG. 2 is a view of the FIG. 1 wafer fragment shown at a processingstage subsequent to that of FIG. 1 in accordance with the exemplaryfirst embodiment aspect.

FIG. 3 is a view of the FIG. 1 wafer fragment shown at a processingstage subsequent to that of FIG. 2 in accordance with the exemplaryfirst embodiment aspect.

FIG. 4 is a diagrammatic, cross-sectional view of a semiconductor waferfragment shown at a preliminary processing stage of an exemplary secondembodiment aspect of the present invention.

FIG. 5 is a view of the FIG. 4 wafer fragment shown at a processingstage subsequent to that of FIG. 4 in accordance with the exemplarysecond embodiment aspect of the present invention.

FIG. 6 is a view of the FIG. 4 wafer fragment shown at a processingstage subsequent to that of FIG. 4 in accordance with an exemplary thirdembodiment aspect of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws “to promote the progressof science and useful arts” (Article 1, Section 8).

One aspect of the invention is a recognition that it can be advantageousto form metal nitride to comprise two different layers, with each of thelayers formed from a different precursor than the other. It can beparticularly advantageous to utilize metal nitride comprising the twodifferent layers when forming the metal nitride proximate a high-kdielectric material (with the term high-k dielectric material referringto a dielectric material having a dielectric constant greater than thatof silicon dioxide). Exemplary high-k dielectric materials are aluminumoxide and hafnium oxide. Two types of precursor that can be utilized forforming metal nitride are halogenated precursor and non-halogenatedmetallo-organic precursor. For instance, titanium nitride can be formedfrom the exemplary halogenated precursor titanium tetrachloride (TiCl₄),or alternatively can be formed from the exemplary non-halogenatedmetallo-organic precursor tetrakis-dimethyl-amido-titanium (TDMAT).Titanium nitride is but one exemplary metal nitride, and other metalnitrides can similarly be formed from halogenated and non-halogenatedprecursors.

Metal nitride formed from halogenated precursor (such as, for example,titanium nitride formed from titanium tetrachloride) is relativelyresistant to oxidation compared to metal nitride formed frommetallo-organic precursors (such as, for example, titanium nitrideformed from TDMAT), and also can be formed relatively rapidly bycommonly-used deposition methods, such as, for example, chemical vapordeposition (CVD) and atomic layer deposition (ALD). However, metalnitride formed from halogenated precursor will frequently have somehalogen incorporated therein (for instance, titanium nitride formed fromtitanium tetrachloride frequently has some chlorine dispersed therein).If the metal nitride formed from a halogenated precursor is formedproximate a dielectric material without an intervening barrier, halogencan permeate from the metal nitride into the dielectric material. Suchpermeation can occur during, for example, deposition and/orpost-deposition steps. The halogen can adversely affect the propertiesof the dielectric material, with the adverse effects being particularlyproblematic relative to high-k dielectric materials.

One aspect of the present invention is to form metal nitride to containtwo portions, with each of the portions being primarily from a differentprecursor than the other. A portion of the metal nitride closest to adielectric material is formed utilizing an metallo-organic precursor,and a portion of the metal nitride further from the dielectric materialis formed utilizing halogenated precursor. The portion of the metalnitride formed from halogenated precursor can protect the portion formedfrom metallo-organic precursor from oxidation, and the portion formedfrom metallo-organic precursor can function as a barrier layer toimpede, and in particular applications entirely prevent, migration ofhalogen from the other portion of the metal nitride into the dielectricmaterial.

The invention described herein can be particularly useful for formingcapacitor constructions, in that capacitor constructions frequently havemetal nitride formed proximate dielectric materials. However, it is tobe understood that the invention is not limited to such applications.Also, although the invention can be particularly useful for utilizationin conjunction with high-k dielectric materials, in that the high-kdielectric materials are typically more severely affected by halogenmigration than are lower-k dielectric materials, it is to be understoodthat the invention can also have advantageous aspects for utilizationwith low-k dielectric materials (with the term low-k dielectric materialreferring to dielectric materials having a dielectric constant equal toor less than that of silicon dioxide). Additionally, although theinvention is described with reference to metal nitride materialscomprising two portions, it is to be understood that the invention alsoincludes aspects in which metal nitride comprises more than twoportions.

An exemplary first embodiment of the present invention is described withreference to FIGS. 1-3. Referring initially to FIG. 1, a semiconductorwafer fragment 10 comprises a substrate 12 having a conductively-dopeddiffusion region 14 therein. Substrate 12 can comprise, for example,monocrystalline silicon lightly doped with background p-type dopant. Toaid in interpretation of the claims that follow, the terms“semiconductive substrate” and “semiconductor substrate” are defined tomean any construction comprising semiconductive material, including, butnot limited to, bulk semiconductive materials such as a semiconductivewafer (either alone or in assemblies comprising other materialsthereon), and semiconductive material layers (either alone or inassemblies comprising other materials). The term “substrate” refers toany supporting structure, including, but not limited to, thesemiconductive substrates described above.

Diffusion region 14 can be formed by implanting conductivity-enhancingdopant into the semiconductive material of substrate 12. Diffusionregion 14 can be a source/drain region of a transistor device, as knownto persons of ordinary skill in the art, and the remainder of suchtransistor device is represented diagrammatically by a box 16 in FIG. 1.

An electrically conductive pedestal 18 is over diffusion region 14.Pedestal 18 can comprise any suitable conductive material, including,for example, metals, metal compounds, conductively-doped silicon, etc.Pedestal 18 has an upper surface 19 which is an electrical node forelectrical connection to a capacitor electrode. In some aspects,pedestal 18 can be omitted.

An electrically insulative material 20 is beside pedestal 18, andelectrically isolates pedestal 18 from other electrically conductivematerials (not shown) which can be formed over substrate 12. Thediagrammatic illustration of FIG. 1 shows insulative material 20 as asingle homogeneous material, but it is to be understood that numerousmaterials can be incorporated into insulative material 20, and furtherthat numerous devices can extend within insulative material 20.

A capacitor electrode 22 is over pedestal 18 and in electricalconnection with pedestal 18. In the shown aspect of the invention,electrode 22 is in direct contact (i.e., touches) upper surface 19 ofpedestal 18. Electrode 22 can comprise any suitable conductive material,or combination of materials, including, for example, metal, metalcompounds, conductively-doped silicon, etc. In particular aspects, theelectrode will comprise rugged silicon (such as hemispherical grainsilicon) and accordingly will comprise a roughened outer surface ratherthan the shown smooth surface.

A dielectric material 24 extends over the outer surface of capacitorelectrode 22. Dielectric material 24 can comprise any suitable material,or combination of materials, including, for example, high-k materialsand/or low-k materials. In particular aspects, capacitor dielectric 24will comprise one or more of aluminum oxide, hafnium oxide, silicondioxide and silicon nitride.

FIG. 2 shows wafer fragment 10 at a processing stage subsequent to thatof FIG. 1. A metal nitride layer 26 is formed over dielectric material24, and in the shown aspect of the invention is formed in direct contactwith dielectric material 24. Metal nitride layer 26 can comprise,consist essentially of, or consist of metal nitride, and in particularaspects will comprise, consist essentially of, or consist of titaniumnitride. Metal nitride layer 26 is formed from a non-halogenatedmetal-containing precursor, preferably in the absence of halogenatedmetal-containing precursor. The non-halogenated precursor can be ametallo-organic precursor, and in some aspects can comprise metal,carbon, hydrogen and nitrogen. For instance, if metal nitride layer 26comprises titanium nitride, such can be formed utilizing TDMAT. Anexemplary process for forming layer 26 is an ALD process utilizing TDMAT(as the source of titanium) and a nitrogen source (such as ammonia). TheALD can be conducted at a temperature of 125° C. Alternatively, layer 26can be formed utilizing CVD with TDMAT and a nitrogen source (such asammonia).

Layer 26 preferably has a thickness of less than or equal to about 20 Å,and in some aspects can be formed to a thickness of from at least about10 Å to less than or equal to about 20 Å. Layer 26 is shown withoutcross-hatching because the conductivity of layer 26 can vary dependingupon the level of oxidation of the layer. As discussed above, metalnitrides formed from metallo-organic precursor materials (such as, forexample, titanium nitride formed from TDMAT) can frequently berelatively easy to oxidize. If layer 26 is sufficiently oxidized, thelayer can be relatively electrically insulative, whereas if the layerdoes not oxidize, or oxidizes to only a low level, the layer will beelectrically conductive.

In some aspects, layer 26 can be formed to be substantially fullyoxidized, and can thus consist essentially of, or consist of metal,oxygen and nitrogen. In one of such aspects, layer 26 can be initiallyformed to consist essentially of, or consist of metal nitride, and thelayer can then be converted to an oxidized material by exposing layer 26to an oxidizing ambient. In another of such aspects, metal nitride layer26 can be formed in the presence of an oxidizing ambient so that thelayer is oxidized as deposited.

Referring next to FIG. 3, an electrically conductive metal nitride layer28 is formed over metal nitride layer 26. Metal nitride layer 28 isformed utilizing a halogenated metal-containing precursor. In particularaspects, layer 28 is formed only from halogenated metal-containingprecursor, and accordingly is formed without utilizing non-halogenatedmetal-containing precursor.

Metal nitride layer 28 is formed over and in direct contact with metalnitride layer 26 in the shown aspect of the invention, and accordinglyis spaced from dielectric material 24 by metal nitride layer 26.

Metal nitride layer 28 can comprise the same metal as metal nitridelayer 26, and in particular aspects, metal nitride layers 26 and 28 willboth consist essentially of, or consist of the same metal nitride. Forinstance, metal nitride layers 26 and 28 can both comprise, consistessentially of, or consist of titanium nitride.

If layer 28 comprises titanium nitride, the layer can be formedutilizing TiCl₄ as a halogenated titanium-containing precursor. Thehalogenated titanium-containing precursor can be utilized in combinationwith ammonia to deposit layer 28, with suitable deposition conditionsbeing CVD conditions or ALD conditions. For instance, layer 28 can beformed utilizing ALD conditions with TiCl₄ and ammonia at processingtemperatures of from about 400° C. to about 600° C. Layer 28 ispreferably much thicker than layer 26, in that the resistance of layer28 to oxidation can allow the conductivity of layer 28 to be bettercontrolled than that of layer 26. Specifically, layer 28 will remainconductive even if exposed to an oxidizing ambient. An exemplarythickness for layer 28 is greater than 100 Å, with typical thicknessesbeing from about 100 Å to about 150 Å.

Layers 26 and 28 can be referred to as a first metal nitride layer and asecond metal nitride layer in the claims that follow. Layer 28 can beincorporated into a second capacitor electrode which is spaced from thefirst capacitor electrode 22 by dielectric material 24. Accordingly, thefirst and second capacitor electrodes, together with dielectricmaterial, can form a capacitor construction. Such capacitor constructioncan be utilized in combination with transistor device 16 as a dynamicrandom access memory (DRAM) unit cell, and can be formed as part of aDRAM array. The metal nitride layer 26 can be considered part of thesecond capacitor electrode if the layer has suitable conductivity, orcan be considered part of the dielectric material if the metal nitrideis sufficiently oxidized to be effectively electrically insulative.

Layers 26 and 28 can be formed in separate reaction chambers from oneanother (i.e., formed ex situ relative one another), or can be formed ina common reaction chamber (i.e., formed in situ relative one another).In particular aspects, layers 26 and 28 can be formed in a common ALD orCVD reaction chamber, with a seal to the chamber not being broken fromthe initiation of formation of layer 26 until completion of formation oflayer 28. For an exemplary CVD process, layer 26 is formed in thereaction chamber by introducing an appropriate non-halogenatedmetal-containing precursor into the reaction chamber in combination witha nitrogen-containing precursor, and, after completion of formation oflayer 26, a halogenated metal-containing precursor is introduced intothe chamber together with an appropriate nitrogen-containing precursorto form layer 28. The non-halogenated precursor utilized to form layer26 can be purged from the chamber prior to introduction of thehalogenated metal-containing precursor. The nitrogen-containingprecursor utilized to form layer 28 can be different than that utilizedto form layer 26 or can be the same. For instance, if layers 26 and 28comprise titanium, the non-halogenated precursor can comprise TDMAT, thehalogenated precursor can comprise TiCl₄, and the nitrogen-containingprecursor can comprise ammonia during both formation of layer 26 andformation of layer 28.

The top capacitor electrode comprising material 28 can, in some aspects,comprise metal nitride material 28 alone, and in other aspects cancomprise material 28 together with a plurality of other conductivelayers (such as layers comprising metal, metal alloys and/orconductively-doped silicon). If material 28 is utilized with a pluralityof other conductive layers, material 28 will typically be in a locationrelative to the other layers such that the metal nitride layer 28directly contacts metal nitride layer 26. The direct contact of layers26 and 28 can allow a common processing chamber to be used for formingthe layers 26 and 28, and in some aspects the chamber can remain sealedfrom initiation of formation of layer 26 until completion of formationof layer 28, as discussed above.

Another aspect of the invention is described with reference to FIGS.4-5. In referring to FIGS. 4-5, similar numbering will be used as wasused above in describing FIGS. 1-3, where appropriate. A semiconductorconstruction 100 is shown in FIG. 4, and such construction comprises thesubstrate 12 and diffusion region 14 described previously. Theconstruction also comprises the transistor device 16, insulativematerial 20, and pedestal 18 described above. Insulative material 20 isshown differently in FIG. 4 than in FIG. 1, in that insulative material20 of FIG. 4 has an uppermost surface which is substantially planar withthe uppermost surface 19 of pedestal 18. Such can be accomplished by forexample, chemical-mechanical planarization. It is to be understood thatthe structure of FIG. 4 is shown to illustrate another potentialconfiguration for methodology of the present invention, and that theconfiguration of insulative material 20 of FIGS. 1-3 could also beutilized in the methodology of FIGS. 4 and 5, or the configuration ofFIG. 4 could be utilized in the aspect of FIGS. 1-3, as will berecognized by a person of ordinary skill in the art.

An electrically-conductive metal nitride layer 102 is formed over uppersurface 19 of pedestal 18, and in the shown aspect of the invention isin direct contact with the upper surface 19. Metal nitride layer 102 isformed using a halogenated metal-containing precursor, and can be formedutilizing identical processing as was described above with reference tometal nitride 28 of FIG. 3.

A metal nitride layer 104 is formed over metal nitride layer 102. Metalnitride layer 104 is formed utilizing non-halogenated metal-containingprecursor, and preferably is formed without halogenated metal-containingprecursor being present. Layer 104 can be formed utilizing identicalprocessing as was described above for formation of layer 26 (FIG. 2).

Referring to FIG. 5, a dielectric material 106 is formed over dielectricmaterial 104, and a capacitor electrode 108 is formed over dielectricmaterial 106. Dielectric material 106 and capacitor electrode 108 cancomprise identical compositions as described above for dielectricmaterial 24 and capacitor electrode 22, respectively (FIGS. 1-3).

The construction of FIG. 5 comprises a capacitor having a firstelectrode which incorporates metal nitride material 102, a secondelectrode 108, and a dielectric material 106 between the first andsecond capacitor electrodes. The metal nitride material 104 can beconsidered part of the first capacitor electrode if the material 104 issuitably conductive, and otherwise can be considered part of thecapacitor dielectric. It is preferred that material 104 be very thin inapplications in which the material 104 is part of a bottom electrode,due to difficulties in controlling the conductive properties of thematerial 104 that has been exposed to conditions utilized for formationof dielectric material on the material 104. Material 104 will typicallybe formed to a thickness of less than or equal to about 10 Å. Material102 can be formed to comparable thicknesses to those discussed abovewith reference to metal nitride 28, and accordingly can have a thicknessgreater than 100 Å, and typically will have a thickness of from about100 Å to about 150 Å.

The bottom capacitor electrode comprising material 102 can, in someaspects, comprise metal nitride material 102 alone, and in other aspectscan comprise material 102 together with a plurality of other conductivelayers (such as layers comprising metal, metal alloys and/orconductively-doped silicon). If material 102 is utilized with aplurality of other conductive layers, the material 102 will typically bean uppermost of the layers so that the metal nitride layers 102 and 104will be in direct contact with one another. The direct contact of layers102 and 104 can allow a common processing chamber to be used for formingthe layers 102 and 104, and in some aspects the chamber can remainsealed from initiation of formation of layer 102 until completion offormation of layer 104.

Metal nitride layers 102 and 104 can be referred to as a first metalnitride layer and a second metal nitride layer, respectively.Utilization of the terms “first metal nitride layer” and “second metalnitride layer” is in a sense reversed in describing the embodiment ofFIG. 5 relative to the description of the embodiment of FIG. 3.Specifically, the metal nitride layer formed utilizing the halogenatedprecursor of FIG. 5 (layer 102) is referred to as a first metal nitridelayer, and the layer formed utilizing the non-halogenatedmetal-containing precursor (layer 104) is referred to as a second metalnitride, whereas in the embodiment of FIG. 3 the layer formed utilizingthe non-halogenated precursor (layer 26) is referred to as a first metalnitride and the layer formed utilizing the halogenated metal-containingprecursor (layer 28) is referred to as a second metal nitride.

Commonality between the embodiment of FIG. 5 and that of FIG. 3 is thata metal nitride is formed proximate a dielectric material (the metalnitride of FIG. 3 comprising layers 26 and 28, and that of FIG. 5comprising layers 102 and 104), with a portion of the metal nitridenearest the dielectric material being formed from a non-halogenatedmetal-containing precursor (the portion 26 of FIG. 3 and the portion 104of FIG. 5), while the portion furthest from the dielectric material isformed from a halogenated metal-containing precursor (the portion 28 ofFIG. 3 and the portion 102 of FIG. 5).

The aspects of FIGS. 1-3 and 4-5 can be combined. Such is described withreference to a semiconductor wafer fragment 200 of FIG. 6. Identicalnumbering is used in FIG. 6 as was utilized above in FIGS. 1-5, wereappropriate.

Construction 200 comprises the substrate 12, diffusion region 14,transistor structure 16, insulative material 20, and pedestal 18described previously. Construction 200 further comprises the metalnitride layers 102 and 104 of FIG. 5, and the dielectric material 106.Additionally, construction 200 comprises the metal nitride layers 26 and28 of FIG. 3. Accordingly, construction 200 comprises a capacitor devicein which a first electrode comprises metal nitride layer 102 and asecond electrode comprises metal nitride layer 28, with layers 102 and28 both being formed utilizing halogenated metal-containing precursor.The layers 102 and 28 are separated from dielectric material 106 by themetal nitride layers 104 and 26 formed from non-halogenated precursor.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

1. A semiconductor construction, comprising: a semiconductor substrate; a first capacitor electrode supported by the semiconductor substrate; a second capacitor electrode supported by the semiconductor substrate and capacitively coupled with the first capacitor electrode; capacitor dielectric between the first and second capacitor electrodes; wherein the first capacitor electrode comprises a layer consisting essentially of metal nitride, said layer being directly against the capacitor dielectric; wherein the capacitor dielectric comprises a first composition and a second composition different from the first composition; the second composition being between the first composition and first capacitor electrode, and being directly against the first composition and the layer consisting essentially of metal nitride; the second composition consisting essentially of metal, oxygen and nitrogen; wherein the second composition has a thickness of less than or equal to about 20 Å; wherein the layer consisting essentially of metal nitride has a thickness of at least about 100 Å; and wherein the first composition comprises one or both of aluminum oxide and hafnium oxide.
 2. The construction of claim 1 wherein the second composition consists essentially of titanium, nitrogen and oxygen.
 3. The construction of claim 1 wherein: the layer consisting essentially of metal nitride comprised by the first capacitor electrode is a first layer consisting essentially of metal nitride; the second capacitor electrode comprises a second layer consisting essentially of metal nitride, said second layer being directly against the capacitor dielectric; and the capacitor dielectric comprises a third composition between the first composition and second capacitor electrode, and being directly against the first composition and the second layer; the third composition consisting essentially of metal, oxygen and nitrogen.
 4. The construction of claim 3 wherein the third composition is compositionally the same as the second composition.
 5. A capacitor, comprising: a first capacitor electrode comprising a first region consisting of titanium nitride; a lower dielectric layer over and directly against the titanium nitride of the first region, the lower dielectric layer consisting of titanium, nitrogen and oxygen; at least one intermediate dielectric layer over the lower dielectric layer; an upper dielectric layer over the at least one intermediate dielectric layer, the upper dielectric layer consisting of titanium, nitrogen and oxygen; a second capacitor electrode over the upper dielectric layer, the second capacitor electrode comprising a second region consisting of titanium nitride, the titanium nitride of the second region being over and directly against the upper dielectric layer; wherein the at least one intermediate dielectric layer comprises one or both of aluminum oxide and hafnium oxide; wherein the lower dielectric layer has a thickness of less than or equal to about 20 Å; wherein the upper dielectric layer has a thickness of less than or equal to about 20 Å; wherein the first region has a thickness of at least about 100 Å; and wherein the second region has a thickness of at least about 100 Å. 